The dual and multi-flow pipe invention herein is intended for, and adapted specifically for, use in the particular methods of hydrocarbon recovery from underground hydrocarbon formations,
Specifically, the dual and multi-flow pipe members forming the subject matter of the present invention are particularly suited for the methods of hydrocarbon recovery set out and claimed in PCT patent application WO 2015/00071 and WO 2015/00072. PCT 2015/00072 in particular describes a particular method of hydrocarbon recovery which involves injection of a flushing fluid into multiple parallel alternate spaced-apart fractures along a wellbore drilled in a hydrocarbon formation, and at the same time recovering hydrocarbons from an adjacent alternately-spaced fracture(s) along such wellbore. Such methods using a single wellbore but involving two separate fluids thus require dual or multi-flow pipe capable of delivering the flushing fluid, typically under high pressure, to alternately spaced fractures along the wellbore, while at the same time being able to recover hydrocarbons draining into the wellbore from remaining spaced apart (alternately spaced) fractures and allow same to be produced to surface (hereinafter referred to as the “fracture-flow” process).
It is a difficult technical problem to design a dual or multi-flow pipe assembly comprised of individual pipe segments joined together which is capable of easy manufacture and assembly and which may be used in the fracture-flow process, but which at the same time can achieve the objectives of keeping such two fluids separate and without leakage between flow channels and/or at pipe coupling joints.
Prior art techniques for maintaining two separate fluid flows or channels within a single wellbore typically employ two separate pipe members within such single wellbore (the so called “dual tube” configuration). The “dual tube” configuration poses significant problems for packer elements capable of sealing around two separate pipe members, as well as between the pipe members and the wellbore or wellbore casing. Typically, packer elements are only adapted to seal around the circumference of a single pipe member and the wellbore, or between the single pipe member and the wellbore lining/casing. Having two separate pipe members within a wellbore introduces significant problems for the packer elements to effectively seal between each of the two separate pipe members and as well between each of the two pipe members and the wellbore. While it has been done in the prior art, the packer members are more complex and expensive to manufacture. As well, the combined cross-sectional area of the separate flow passages is generally less than for a tube-in-tube configuration, or for a single divided tube.
Applicant's commonly assigned PCT application WO 2015/00071 (corresponding to applicant's Canadian Patent Application CA 2,835,592) discloses the desirability of a multi-flow channels using one or more divider partitions for creating the separate flow channels for and within continuous tubing, thus avoiding the problem of how to effectively use and couple discrete pipe elements together when using individual segments of pipe as the production piping. To be clear, applicant's PCT application WO2015/00071 makes no disclosure of how to couple pipe members together without leakage, nor how to ensure flow passages carrying separate fluids stay aligned when the individual pipe segments are coupled together.
The below provided background information and description of prior publications is provided for the purpose of making known information believed by the applicant to be of possible relevance to the present invention relating to a pipe-in-pipe configuration and a single divided pipe. No admission is necessarily intended, nor should be construed, that any of the below publications and information provided constitutes prior art against the present invention.
U.S. Pat. No. 1,781,091 entitled “Pipe Joint” teaches the concept of joining single-flow pipe members using a left hand and right hand reverse thread in the coupling collar, with a buttress joint, as shown in FIG. 4 thereof, to allow the pipe joint to transmit torque in both directions It makes no disclosure as to how such coupling could be adapted for dual or multi-channel pipe assemblies.
U.S. Pat. No. 4,397,484 entitled “Locking Coupling System” teaches a coupling system having two pipe members, each having significantly different pitched threads, one “coarser” than the other, and a “spleened” (sic) coupling with includes two coupling halves each having spleened (sic) ends adapted to lock into each other.
U.S. Pat. No. 3,680,631 entitled “Well Production Apparatus”, teaches inter alia tubing or other pipe which is provided with a vacuum chamber within such pipe, to allow producing a warm fluid through the centre of the pipe when the pipe/wellbore passes through a zone of permafrost.
U.S. Pat. No. 2,204,392 entitled “Hose and Pipe Coupler” teaches same, and in particular teaches a coupler with a series of grooves or indentations 9, 10 or alternatively 8a, which provide alignment of the two separate halves in order to effect coupling.
U.S. Pat. No. 1,583,126 entitled “Leakage Tight Joint” teaches a pipe coupling for a pair of pipe members, having a coupling nut “a” with different sized and “handed” threads, and a packing ring “c’ of softer material.
U.S. Pat. No. 2,913,261 entitled “Tube Couplings” teaches a pair of exteriorly threaded elements secured to the pipe or tube ends respectively, upon which the coupling members are rotatable into abutting relation. The threads of each element run in opposite directions from each other, and have alternately arranged or staggered lugs to prevent relative rotation when brought into engagement. No apparatus for coupling of co-axial dual flow or multi-flow pipe is disclosed.
U.S. Pat. No. 3,015,500 entitled “Drill String Joint” teaches a pair of frusto-conical threads at opposite ends of pipe members which are desired to be coupled together, having an overlying sleeve member 68.
U.S. Pat. No. 3,762,745 entitled “Connection Members with High Torque Carrying Capacity”, similar to U.S. Pat. No. 4,397,484 above, teaches an externally threaded tubular member, having a pair of threads thereon of different pitch, as well as some additional tooth members for assisting in transmitting torque, and an alignment means for aligning the teeth (locking means) for engagement.
U.S. Pat. No. 861,828 entitled “Pipe Coupling” teaches a male coupling member C, having an internal and an external thread thereon, and a complementary female coupling member D, having a pair of internal threads thereon, as shown in the sole figure thereof. No means of coupling a co-axial pipe is disclosed, or any manner of supporting a co-axial pipe therein.
U.S. Pat. No. 572,124 entitled “Insulated Joint for Light Fixtures”, insofar as may be said to be relevant to the present invention, teaches a joint having upper and lower tubular connecting sections A, C, and an insulating section E.
Finally, U.S. Pat. No. 3,943,618 entitled “Method of Assembly of a Dual-walled Pipe” teaches an outer pipe 1 with a concentric inner pipe 2 defining annulus 3 therebetween. The pipes 1,2 having connector means 32 associated with first pipe are rigidly maintained in this spaced-apart relation by means of connector means 4, 5. FIG. 4 thereof shows an embodiment where inner pipe 20 and outer pipe 21 are connected by way of connector means 22 in a threaded manner, outer pipe 21 having a collar 23 also threaded thereto. Threads 24 between outer surface of pipe 20 and the inner surface of connector means 22 are tapered, wherein thread 25 between the inner surface of pipe 21 and the outer surface of connector means 22 are straight. FIG. 5 shows an embodiment where the second pipe 31 has threads of opposite rotational direction at its opposing ends.
Despite the above prior art, a need exists for a dual or multi-flow pipe assembly using discrete pipe segments, which can be easily manufactured at relatively low cost and further easily joined together in the field and which effectively operates to maintain separate flows of fluid therewithin without leakage.